Research progress in environmental control key technologies, facilities and equipment for laying hen production in China

Abstract: Poultry industry is increasing constantly at the level of scale, intensity, and industrialized production in last 40 years. Environmental factors have become much more significant effects on laying hen, due to the high-yielding layer needs much higher requirement for the comfortable thermal environment, while the low adaptability to environmental fluctuating conditions. Maintaining a suitable living environment conditions, such as temperature, relative humidity, CO2 and NH3, is essential for the birds to ensure their well-being, ef?cient utilization of feed, and the maximum productivity. Large ?uctuations of air temperature can pose multiple adverse effects on bird health, resulting in considerable losses in egg production. Thus, the key factors, including the uniformity of hygro-thermal parameters, and air quality, can affect poultry health, even to increase the bird mortality. In this study, three main aspects were reviewed: environmental regulation theory, environmental control technology, together with the facilities and equipment of poultry farming. The breakthrough was addressed on the thermal insulation performance of outer building envelope, wet-pad evaporative cooling system, ventilation system, and air distribution theory in closed layer house. (1) The laying hen are usually kept in isolated houses with a well-insulated structure, where the thermoneutral temperature can generally be maintained using sensible heat from the birds. Currently, it is becoming increasingly obvious that the layers houses need more insulation to retain heat in cold climates. In order to reduce heat loads in livestock buildings, the optimization of thermal insulation thicknesses of building envelopes can offer an effective way to ensure thermal comfort environment, while to significantly decrease the energy requirements. (2) The ventilation systems also play an important role in reducing excessive heat, moisture, air pollutants, and airborne pathogens in poultry facilities. Generally, the ventilation system is developed to make the fresh air go through a surge chamber before entering the houses. A new ventilation system was designed to alleviate the variations of air temperature for the uniformity, while reduce dust deposition rates in poultry houses, particularly that located in continental climate regions. The wet-pad evaporative cooling system was summarized in different climate zones, including the control of temperature uniformity, and the air distribution technology of poultry houses. (3) The development and application of current facilities and equipment were addressed for poultry housing system, including high density caged system, natural mating colony cages, even the poultry buildings with a slightly acidic electrolyzed water ionizer. The future development direction was predicted on intelligent livestock management and monitoring platform, intelligent caged dead layer identification devices, as well as the welfare-oriented breeding mode and technical equipment for laying hen. This review can provide a theoretical basis for automatically environmental control of large-scale poultry farming, and thereby to promote the high-quality transformation, for the sustainable development of modern poultry stocking industry.